Crystal structure elucidation of a geminal and vicinal bis­(tri­fluoro­methane­sulfonate) ester

Pickl, T.; Zuber, J.; Stephan, J.; Pöthig, A.

doi:10.1107/S2053229624005230

research papers

STRUCTURAL
CHEMISTRY

ISSN: 2053-2296

Volume 80| Part 7| July 2024| Pages 278-283

https://doi.org/10.1107/S2053229624005230

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Crystal structure elucidation of a geminal and vicinal bis(trifluoromethanesulfonate) ester

Thomas Pickl,^a Julian Zuber,^a Johannes Stephan ^a and Alexander Pöthig ^a ^*

^aSchool of Natural Sciences & Catalysis Research Center (CRC), Technische Universität München, Ernst-Otto-Fischer Strasse 1, 85748 Garching, Germany
^*Correspondence e-mail: alexander.poethig@tum.de

Edited by T. Ohhara, J-PARC Center, Japan Atomic Energy Agency, Japan (Received 8 April 2024; accepted 3 June 2024; online 14 June 2024)

Geminal and vicinal bis(trifluoromethanesulfonate) esters are highly reactive alkylene synthons used as potent electrophiles in the macrocyclization of imidazoles and the transformation of bypyridines to diquat derivatives via nucleophilic substitution reactions. Herein we report the crystal structures of methylene (C₃H₂F₆O₆S₂) and ethylene bis(trifluoromethanesulfonate) (C₄H₄F₆O₆S₂), the first examples of a geminal and vicinal bis(trifluoromethanesulfonate) ester characterized by single-crystal X-ray diffraction (SC-XRD). With melting points slightly below ambient temperature, both reported bis(trifluoromethanesulfonate)s are air- and moisture-sensitive oils and were crystallized at 277 K to afford two-component non-merohedrally twinned crystals. The dominant interactions present in both compounds are non-classical C—H⋯O hydrogen bonds and intermolecular C—F⋯F—C interactions between trifluoromethyl groups. Molecular electrostatic potential (MEP) calculations by DFT-D3 helped to quantify the polarity between O⋯H and F⋯F contacts to rationalize the self-sorting of both bis(trifluoromethanesulfonate) esters in polar (non-fluorous) and non-polar (fluorous) domains within the crystal structure.

Keywords: crystal structure; bis(trifluoromethanesulfonate); geminal ditriflate; vicinal ditriflate; sensitive oil.

CCDC references: 2360162; 2360161

1. Introduction

Trifluoromethanesulfonate (triflate) is an important functional group in organic chemistry owing to its strong electron-withdrawing nature (Howells & McCown, 1977 ; Hendrickson et al., 1977 ). It is an excellent leaving group used in many organic transformations, such as nucleophilic substitutions, due to the extreme stability of the liberated triflate anion (OTf⁻). Thus, the derived triflyl esters (R–OTf) are potent electrophiles, representing a halogen-free alternative to alkyl halides in nucleophilic substitution reactions.

Pushing the reactivity of these compounds to an extreme, two triflate groups can be attached to the same carbon to form geminal bis(triflate) esters with the general formula TfO–CR₂–OTf (Martínez et al., 1979 , 1987 ). Among other landmark examples, the parent compound methylene bis(triflate) (1, R = H) had already been reported in 1980 (Katsuhara & DesMarteau, 1980 ) but has not been used in chemical synthesis until several decades later. As a highly reactive C1 synthon, the electrophilicity of 1 was eventually harnessed to construct large cyclophanes via nucleophilic substitution reactions (Anneser et al., 2015 ), particularly in cases where bis(imidazoles) were macrocyclized to methylene-bridged tetra(imidazolium) salts (Altmann et al., 2015 , 2016 ; Bernd et al., 2020 ).

Similarly, the ethylene-bridged bis(triflate) ester TfO–(CH₂)₂–OTf (2) has been commonly used as a bis-alkylating reagent (C2 synthon), among others, for the transformation of bipyridines to diquat derivatives (Coe et al., 2006 ) and for the synthesis of ethylene-bridged metal complexes (Lindner et al., 1990 ) or η²-olefin metal complexes (Lindner et al., 1985 ).

Investigating the structure–property relationship of geminal and vicinal bis(sulfonate) esters, such as compounds 1 and 2, respectively, is imperative to gain a better understanding of their reactivity. In this regard, a structural comparison of similar alkylene bis(mesylates) used as DNA crosslinking agents has been reported, which includes the parent compound MsO–(CH₂)₂–OMs (3, Ms = mesyl or methanesulfonyl) (McKenna et al., 1989 ). So far, this study has been complemented by the structural characterizations of only a few other vicinal bis(mesylate) and bis(tosylate) derivatives, such as TsO–(CH₂)₂–OTs (4, Ts = tosyl or toluenesulfonyl) (Groth et al., 1985 ), and a handful of geminal bis(tosylates) (Kamal et al., 2020 ).

To date, however, there are no reports on the molecular structures of geminal or vicinal bis(triflate) esters, such as the title compounds 1 and 2 (see Scheme 1). Aiming to study the structure–reactivity relationship of these alkylene sources, we synthesized both compounds and characterized them in the solid state by single-crystal X-ray diffraction (SC-XRD).

2. Experimental

2.1. Synthesis and crystallization

Sulfonate esters 1 and 2 were prepared according to established procedures. Methylene bis(triflate) (1) was synthesized by heating an equimolar suspension of triflic anhydride and paraformaldehyde to 353 K, causing the liberation of formaldehyde, which was further reacted with the anhydride at the same temperature for 16 h. Following the evaporation of excess triflic anhydride in vacuo, the crude product was passed over a short plug of silica with dichloromethane as the eluent. After removal of all volatiles at 293 K under reduced pressure, analytically pure 1 was obtained as a colourless-to-brown oil. The yields of this reaction typically range between 15 and 20%, which is consistent with previous reports (Anneser et al., 2015).

There are several approaches for the preparation of ethylene bis(triflate) (2), e.g. the straightforward transmetalation of ethylene dibromide with AgOTf (Shackelford et al., 1985 ). However, for the purpose of this study, the reaction of ethylene glycol with triflic anhydride under basic conditions was chosen as the preferred method because the diol is readily available and inexpensive, and the desired product is usually obtained in close to quantitative yields (Kuroboshi et al., 2015 ). To equimolar amounts of triflic anhydride and pyridine in dichloromethane was added half an equivalent of ethylene glycol at 273 K. The reaction mixture was stirred at the same temperature for 45 min, filtered and washed several times with water. The organic layer was dried over sodium sulfate, filtered and concentrated under reduced pressure. The crude product was filtered over a short plug of silica with dichloromethane as the eluent. All volatiles were subsequently removed at 293 K under reduced pressure to afford analytically pure 2 as a colourless oil (81% yield).

Bis(triflates) 1 and 2 are air- and water-sensitive liquids at ambient temperature, with melting points between 278 and 288 K (Lindner et al., 1981 ; Anneser et al., 2015). Single crystals were grown by allowing the compounds to solidify slowly over the course of several hours at a temperature of 277 K. To prevent the obtained crystals from melting immediately during picking, the tools used in the process were cooled by repeatedly submerging them in a Dewar flask filled with liquid nitrogen. Additionally, a piece of dry ice was placed on the microscope slide to delay the melting of the specimen on the glass. The selected crystals were then mounted on top of a Kapton micro sample holder (MicroMount) coated with perfluorinated ether and rapidly transferred to the diffractometer.

2.2. Refinement

Data collection and structure refinement details are summarized in Table 1. As implemented in APEX4 (Bruker, 2022 ), the non-merohedral twinning of 1 and 2 was addressed by integration of the diffraction data using two orientation matrices in SAINT (Bruker, 2019 ), followed by scaling and absorption correction with TWINABS (Bruker, 2012 ). The structures were solved by SHELXT (Sheldrick, 2015a ) and refined against the respective HKLF5 files using SHELXL (Sheldrick, 2015b ) in conjunction with ShelXle (Hübschle et al., 2011 ). All non-H atoms were refined with anisotropic displacement parameters. H atoms could be located in difference Fourier maps, but for the refinement were positioned geometrically and refined using a riding model, with C—H = 0.99 Å and U_iso(H) = 1.2U_eq(C).

Table 1
Experimental details

Experiments were carried out at 100 K with Mo Kα radiation using a Bruker D8 VENTURE diffractometer. Absorption was corrected for by multi-scan methods (TWINABS; Bruker, 2012). H-atom parameters were constrained.

	(1)	(2)
Crystal data
Chemical formula	C₃H₂F₆O₆S₂	C₄H₄F₆O₆S₂
M_r	312.17	326.19
Crystal system, space group	Monoclinic, P2₁	Triclinic, P $[\overline{1}]$
a, b, c (Å)	8.9822 (12), 4.9413 (6), 10.9400 (14)	10.036 (4), 10.664 (3), 11.276 (4)
α, β, γ (°)	90, 102.406 (5), 90	83.540 (9), 64.178 (9), 89.593 (9)
V (Å³)	474.22 (11)	1078.2 (6)
Z	2	4
μ (mm⁻¹)	0.68	0.60
Crystal size (mm)	0.35 × 0.32 × 0.06	0.16 × 0.09 × 0.01

Data collection
T_min, T_max	0.540, 0.746	0.564, 0.745
No. of measured, independent and observed [I > 2σ(I)] reflections	2295, 2295, 2254	4339, 4339, 3403
R_int	0.044	0.079
(sin θ/λ)_max (Å⁻¹)	0.667	0.625

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.027, 0.072, 1.05	0.066, 0.166, 1.07
No. of reflections	2295	4339
No. of parameters	155	326
No. of restraints	1	0
Δρ_max, Δρ_min (e Å⁻³)	0.41, −0.47	0.60, −0.55
Absolute structure	Flack x determined using 959 quotients [(I⁺) − (I⁻)]/[(I⁺) + (I⁻)] (Parsons et al., 2013)	–
Absolute structure parameter	0.12 (4)	–
Computer programs: APEX4 (Bruker, 2022), SAINT (Bruker, 2019), SHELXT (Sheldrick, 2015a), SHELXL (Sheldrick, 2015b), ShelXle (Hübschle et al., 2011), PLATON (Spek, 2020 ), enCIFer (Allen et al., 2004 ) and FinalCif (Kratzert, 2023 ).

2.3. DFT calculations

All density functional theory (DFT) calculations were performed with the ORCA quantum chemistry package (Version 5.0.4; Neese, 2012 , 2022 ) using the PBE0 exchange-correlation functional (Adamo & Barone, 1999 ) and the def2-TZVP triple-ξ valence basis set (Weigend & Ahlrichs, 2005 ), as implemented in ORCA. Tighter than normal convergence criteria for SCF calculations (TightSCF) and geometry optimizations (TightOPT) were employed. Grimme's atom-pairwise dispersion correction with the Becke–Johnson damping scheme (D3BJ) was applied to account for dispersion interactions (Grimme et al., 2010 , 2011 ). Geometries were optimized in the gas phase without symmetry constraints. The starting geometries were derived from the SC-XRD structures of 1 and 2. Frequency analysis at the same level of theory as the geometry optimizations confirmed that the calculations had converged to an energetic minimum. To calculate the molecular electrostatic potentials (MEPs), the total SCF density file obtained after a PBE0/def2-TZVP single-point calculation was first converted to a Gaussian cube file using the orca_plot module implemented in the ORCA package. The MEP was then calculated using the orca-vpot module and exported in Gaussian cube format. With both cube files in hand, the total SCF density was plotted and the MEP was mapped as a colour onto the isosurface in Molekel (Version 4.3; Varetto, 2002 ).

3. Results and discussion

Sulfonate esters 1 and 2 both crystallized as two-component non-merohedral twins, and their asymmetric units contain one and two crystallographically independent molecules, respectively (Figs. 1 and 2). Methylene bis(triflate) (1) was found to crystallize in the monoclinic space group P2₁ (No. 4, Z = 2), and the fractional contribution of the minor twin component was refined to 29% in the final model. Ethylene bis(triflate) (2) crystallized in the triclinic space group P $[\overline{1}]$ (No. 2, Z = 4) with a 37% contribution of the minor twin component. While both triflic esters are achiral in solution, as indicated by a single ¹H NMR resonance for the CH₂ protons (Salomon & Salomon, 1979 ; Katsuhara & DesMarteau, 1980), bis(triflate) 1 appears to be conformationally locked in the solid state and consequently crystallizes in the Sohncke space group P2₁. Since sulfur is the heaviest atom of the molecule and molybdenum radiation was used in the diffraction experiment, the absolute structure could only be determined with low accuracy. This is reflected by a Flack parameter of 0.12 with a comparably large standard uncertainty (Flack, 1983 ; Parsons et al., 2013 ). In contrast to bis(triflate) 1, ethylene derivative 2 crystallizes in a centrosymmetric space group (P $[\overline{1}]$ ) and the asymmetric unit contains two symmetry-independent conformers of the molecule, which differ mainly in the relative orientation of a triflate group, as expressed by different C—C—O—S torsion angles (Fig. 3). A comparison of the bond distances of both esters reveals almost identical values for chemically equivalent C—F, C—S and terminal S—O bonds, while the average C—O distance is slightly shorter in 1 (1.434 Å) compared to 2 (1.481 Å). In contrast, the mean bond length of the adjacent S—O bond is elongated in 1 (1.573 Å) versus 2 (1.547 Å).

Figure 1
View of methylene bis(trifluoromethanesulfonate) (1) with the atom-numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 30% probability level.

Figure 2
View of both symmetry-independent conformers of ethylene bis(trifluoromethanesulfonate) (2) with the atom-numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 30% probability level.

Figure 3
Overlay of the two symmetry-independent conformers of 2, highlighting the different relative orientations of a trifluoromethanesulfonate group as quantified by different C—C—O—S torsion angles. For clarity, the conformers are drawn in ball-and-stick representation in red and grey, respectively.

The packing of bis(triflates) 1 and 2 is primarily influenced by non-classical C—H⋯O hydrogen bonds between methylene and sulfonate groups, along with intermolecular C—F⋯F—C interactions between trifluoromethyl residues closer than the sum of the van der Waals radii (Haynes, 2015 ) (Tables 2–5 ). This interaction pattern results in the formation of two-dimensional fluorous and non-fluorous domains in the crystal packing of 1 and 2 (Figs. 4 and 5). Considering this emergence of polar and non-polar domains, we aimed to quantify the influence of differently polarized regions within both structures on the overall solid-state arrangement of the bis(triflates). Therefore, we calculated the molecular electrostatic potentials (MEPs) of 1 and 2 based on the optimized geometries of the respective monomers using DFT-D3 in the gas phase (Fig. 6). As expected, in both cases, the triflate O atoms are the most negatively charged, followed by the F atoms of the CF₃ groups. In stark contrast, the CH₂ fragments of methylene and ethylene bis(triflate) exhibit a high positive charge, which is consistent with their experimentally observed reactivity as strong electrophiles. Along this line, hydrogen-bonding interactions occur only between highly charged parts of both bis(triflates), namely, positively polarized alkylene H and negatively polarized sulfonate O atoms. The trifluoromethyl groups, with a lower C—F bond polarization, do not participate in hydrogen bonding. Instead, they establish fluorous domains whose arrangement in the crystal is governed by the orientation of the CF₃ groups within the monomers. In methylene bis(triflate) (1), these groups align in a shared direction, whereas in ethylene bis(triflate) (2), they assume opposite orientations in the molecule. The emerging regions of different polarity within the molecules are thus caused by the observed self-sorting of 1 and 2 into highly polar and nonpolar domains within the crystal structure.

Table 2
Hydrogen-bond geometry (Å, °) for 1

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1⋯O2	0.99	2.32	2.803 (6)	109
C1—H2⋯O6	0.99	2.29	2.802 (6)	111
C1—H1⋯O3ⁱⁱⁱ	0.99	2.51	3.416 (5)	152
C1—H2⋯O5^iv	0.99	2.56	3.430 (5)	147
Symmetry codes: (iii) $[-x+2, y-{\script{1\over 2}}, -z+1]$ ; (iv) $[-x+1, y-{\script{1\over 2}}, -z+1]$ .

Table 3
Selected interatomic distances (Å) for 1

F3⋯F6ⁱ	2.894 (5)	F4⋯F5ⁱ	2.957 (3)
F1⋯F5ⁱⁱ	2.933 (4)
Symmetry codes: (i) $[-x+1, y-{\script{1\over 2}}, -z]$ ; (ii) .

Table 4
Hydrogen-bond geometry (Å, °) for 2

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2B⋯O8ⁱ	0.99	2.62	3.60 (1)	172
C3—H3A⋯O1ⁱⁱⁱ	0.99	2.60	2.984 (9)	103
C3—H3B⋯O1ⁱⁱⁱ	0.99	2.59	2.984 (9)	104
C3—H3A⋯O8^iv	0.99	2.59	3.579 (8)	175
C6—H6A⋯O6^v	0.99	2.34	3.092 (8)	132
C6—H6A⋯O11^vi	0.99	2.47	3.034 (8)	116
C6—H6B⋯O2^vii	0.99	2.45	3.210 (8)	133
C7—H7A⋯O5^vii	0.99	2.49	3.365 (8)	147
C7—H7B⋯O7^viii	0.99	2.70	3.525 (7)	142
C7—H7B⋯O2^iv	0.99	2.54	3.349 (9)	139
Symmetry codes: (i) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) ; (viii) .

Table 5
Selected interatomic distances (Å) for 2

F5⋯F7	2.823 (7)	F3⋯F9ⁱⁱ	2.954 (5)
F7⋯F12ⁱ	2.951 (7)
Symmetry codes: (i) ; (ii) .

Figure 4
Packing of methylene bis(trifluoromethanesulfonate) (1), showing alternating two-dimensional layers of fluorous and non-fluorous domains along the c axis. The share of these domains of different polarity is indicated by the distances d_n and d_p, respectively.

Figure 5
Packing of ethylene bis(trifluoromethanesulfonate) (2), showing alternating two-dimensional layers of fluorous and non-fluorous domains along the c axis. The share of these domains of different polarity is indicated by the distances d_n and d_p, respectively.

Figure 6
Molecular electrostatic potential (MEP) projected onto the total electron-density surface of (a) methylene (1) and (b) ethylene bis(trifluoromethanesulfonate) (2). Geometries are optimized by DFT-D3 at the PBE0/def2-TZVP level of theory and MEPs are shown at 0.0062 a.u. electron density.

To quantify the share of these alternating domains within the crystal lattice of 1 and 2, alternating planes parallel to the ab plane were defined by (i) all trifluoromethyl C atoms or (ii) all S atoms of each crystallographically independent molecule contained in the unit cell of both structures. Consequently, the separation of polar and non-polar regions was estimated by calculating the distance between two adjacent planes defined by the S atoms (d_p) or C atoms (d_n) for each crystallographically independent molecule (cf. Figs. 4 and 5). For compound 2, the final d_p and d_n values were defined as the average of the individual values of each conformer in the asymmetric unit. For a more detailed definition of the interplanar distances d_p and d_n, see Fig. S1 in the supporting information. In both structures, the polar region was estimated to be larger than the non-polar (compound 1: d_p ≃ 3.8 Å, d_n ≃ 3.5 Å; compound 2: d_p ≃ 3.7 Å, d_n ≃ 2.8 Å). Interestingly, the determined share of the polar domain in 2 is slightly smaller than in 1, even though, compared to methylene bis(triflate) (1), ethylene congener 2 contains an additional CH₂ group acting as a hydrogen-bond donor. Further, the somewhat smaller (polar and non-polar) domain sizes of 2 versus 1 suggest tighter packing of ethylene bis(triflate) in general. As an overarching trend, this rough estimation of domain size also indicates that roughly the same share can be attributed to the non-fluorous and fluorous regions in both bis(triflate) structures.

4. Conclusion

The first comprehensive structural analysis of a geminal and vicinal bis(triflate) ester, specifically methylene (1) and ethylene bis(triflate) (2), is presented. Both compounds are air- and moisture-sensitive oils under ambient conditions and at low temperature crystallized as non-merohedral two-component twins. The crystal structures reveal the presence of non-classical C—H⋯O hydrogen bonds and intermolecular C—F⋯F—C interactions, which govern the packing of the compounds in the solid state. Molecular electrostatic potential (MEP) calculations of monomers 1 and 2 based on DFT-D3 showed that these interactions are driven by the high polarity of the O⋯H contacts and the low polarity of the halogen–halogen contacts, respectively. As a result, bis(triflates) 1 and 2 self-sort in polar (non-fluorous) and non-polar (fluorous) domains of roughly the same relative size within the crystal lattice.

Supporting information

CCDC references: 2360162; 2360161

Crystal structure: contains datablocks global, 2, 1. DOI: https://doi.org/10.1107/S2053229624005230/oj3019sup1.cif

Structure factors: contains datablock 1. DOI: https://doi.org/10.1107/S2053229624005230/oj30191sup2.hkl

Structure factors: contains datablock 2. DOI: https://doi.org/10.1107/S2053229624005230/oj30192sup3.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2053229624005230/oj30191sup4.cdx

Supporting information file. DOI: https://doi.org/10.1107/S2053229624005230/oj30192sup5.cdx

Supporting information file. DOI: https://doi.org/10.1107/S2053229624005230/oj30191sup6.cml

Supporting information file. DOI: https://doi.org/10.1107/S2053229624005230/oj30192sup7.cml

Packing of the title compounds. DOI: https://doi.org/10.1107/S2053229624005230/oj3019sup8.pdf

Computing details top

Methanediyl bis(trifluoromethanesulfonate) (1) top

Crystal data top

C₃H₂F₆O₆S₂	D_x = 2.186 Mg m⁻³
M_r = 312.17	Melting point: 289 K
Monoclinic, P2₁	Mo Kα radiation, λ = 0.71073 Å
a = 8.9822 (12) Å	Cell parameters from 5142 reflections
b = 4.9413 (6) Å	θ = 2.3–28.2°
c = 10.9400 (14) Å	µ = 0.68 mm⁻¹
β = 102.406 (5)°	T = 100 K
V = 474.22 (11) Å³	Plate, colourless
Z = 2	0.35 × 0.32 × 0.06 mm
F(000) = 308

Data collection top

Bruker D8 VENTURE diffractometer	2295 independent reflections
Radiation source: TXS rotating anode	2254 reflections with I > 2σ(I)
Helios optic monochromator	R_int = 0.044
Detector resolution: 16 pixels mm^-1	θ_max = 28.3°, θ_min = 2.3°
ω and φ scans	h = −11→11
Absorption correction: multi-scan (TWINABS; Bruker, 2012)	k = −6→6
T_min = 0.540, T_max = 0.746	l = −14→14
2295 measured reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.027	H-atom parameters constrained
wR(F²) = 0.072	w = 1/[σ²(F_o²) + (0.0318P)² + 0.3843P] where P = (F_o² + 2F_c²)/3
S = 1.05	(Δ/σ)_max < 0.001
2295 reflections	Δρ_max = 0.41 e Å⁻³
155 parameters	Δρ_min = −0.47 e Å⁻³
1 restraint	Absolute structure: Flack x determined using 959 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.12 (4)

Special details top

Experimental. Diffractometer operator T. Pickl scanspeed 1-3 s per frame dx 46 mm 2474 frames measured in 8 data sets phi-scans with delta_phi = 0.5 omega-scans with delta_omega = 0.5 shutterless mode

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refined as a 2-component twin

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
S1	0.96595 (10)	0.4898 (2)	0.31972 (8)	0.0175 (2)
S2	0.44053 (10)	0.4789 (2)	0.32170 (8)	0.01610 (19)
F1	0.7896 (3)	0.1739 (6)	0.1613 (3)	0.0322 (7)
F2	1.0069 (3)	0.2574 (7)	0.1183 (3)	0.0364 (7)
F3	0.8318 (4)	0.5634 (7)	0.0880 (3)	0.0341 (7)
F4	0.4514 (4)	0.4480 (7)	0.0868 (2)	0.0373 (7)
F5	0.5287 (3)	0.8260 (6)	0.1738 (2)	0.0308 (7)
F6	0.2896 (3)	0.7339 (7)	0.1293 (3)	0.0319 (6)
O1	0.8169 (3)	0.6258 (6)	0.3446 (3)	0.0182 (6)
O2	1.0087 (4)	0.2659 (7)	0.3995 (3)	0.0262 (7)
O3	1.0679 (3)	0.7015 (7)	0.3090 (3)	0.0268 (7)
O4	0.6057 (3)	0.3562 (6)	0.3435 (3)	0.0187 (6)
O5	0.3381 (3)	0.2596 (7)	0.3047 (3)	0.0260 (7)
O6	0.4345 (4)	0.6917 (7)	0.4070 (3)	0.0229 (6)
C1	0.7303 (5)	0.4932 (13)	0.4231 (3)	0.0230 (6)
H1	0.795251	0.361855	0.478791	0.028*
H2	0.691600	0.627764	0.475688	0.028*
C2	0.8932 (5)	0.3618 (10)	0.1609 (4)	0.0229 (9)
C3	0.4270 (5)	0.6309 (9)	0.1666 (4)	0.0229 (8)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S1	0.0112 (4)	0.0210 (4)	0.0202 (4)	0.0007 (4)	0.0033 (4)	−0.0024 (5)
S2	0.0115 (4)	0.0185 (4)	0.0186 (4)	0.0011 (5)	0.0038 (3)	0.0015 (5)
F1	0.0281 (15)	0.0359 (16)	0.0334 (13)	−0.0131 (12)	0.0085 (12)	−0.0131 (12)
F2	0.0279 (15)	0.051 (2)	0.0345 (14)	0.0012 (14)	0.0156 (12)	−0.0151 (14)
F3	0.0436 (17)	0.0338 (14)	0.0218 (12)	0.0017 (13)	−0.0001 (12)	0.0042 (10)
F4	0.0454 (17)	0.0465 (19)	0.0206 (11)	0.0085 (17)	0.0083 (11)	−0.0042 (13)
F5	0.0286 (15)	0.0320 (15)	0.0336 (14)	−0.0048 (11)	0.0103 (12)	0.0122 (11)
F6	0.0221 (13)	0.0425 (16)	0.0289 (13)	0.0093 (13)	0.0008 (11)	0.0105 (13)
O1	0.0117 (13)	0.0214 (14)	0.0229 (14)	0.0023 (11)	0.0066 (11)	−0.0006 (11)
O2	0.0246 (16)	0.0269 (17)	0.0266 (15)	0.0108 (14)	0.0043 (13)	0.0047 (13)
O3	0.0188 (15)	0.0306 (17)	0.0331 (16)	−0.0083 (13)	0.0104 (14)	−0.0107 (14)
O4	0.0122 (13)	0.0220 (13)	0.0225 (14)	0.0008 (12)	0.0047 (12)	0.0020 (12)
O5	0.0140 (14)	0.0270 (17)	0.0363 (16)	−0.0021 (12)	0.0036 (13)	0.0039 (14)
O6	0.0212 (15)	0.0249 (15)	0.0228 (14)	0.0065 (13)	0.0049 (12)	0.0000 (13)
C1	0.0121 (13)	0.0387 (19)	0.0182 (13)	−0.0047 (17)	0.0036 (16)	0.000 (2)
C2	0.021 (2)	0.026 (2)	0.0221 (19)	−0.0022 (17)	0.0057 (16)	−0.0054 (17)
C3	0.023 (2)	0.028 (2)	0.0173 (17)	0.0027 (19)	0.0018 (17)	0.0039 (17)

Geometric parameters (Å, º) top

S1—O2	1.410 (4)	F2—C2	1.316 (5)
S1—O3	1.412 (4)	F3—C2	1.321 (6)
S1—O1	1.573 (3)	F4—C3	1.308 (5)
S1—C2	1.833 (4)	F5—C3	1.319 (5)
S2—O5	1.408 (3)	F6—C3	1.316 (5)
S2—O6	1.415 (3)	O1—C1	1.435 (5)
S2—O4	1.573 (3)	O4—C1	1.432 (5)
S2—C3	1.835 (4)	C1—H1	0.9900
F1—C2	1.316 (5)	C1—H2	0.9900

F3···F6ⁱ	2.894 (5)	F4···F5ⁱ	2.957 (3)
F1···F5ⁱⁱ	2.933 (4)

O2—S1—O3	122.5 (2)	O1—C1—H1	110.1
O2—S1—O1	110.91 (17)	O4—C1—H2	110.1
O3—S1—O1	106.8 (2)	O1—C1—H2	110.1
O2—S1—C2	108.1 (2)	H1—C1—H2	108.5
O3—S1—C2	106.4 (2)	F1—C2—F2	109.2 (4)
O1—S1—C2	99.69 (19)	F1—C2—F3	109.3 (4)
O5—S2—O6	122.87 (19)	F2—C2—F3	109.7 (4)
O5—S2—O4	106.97 (19)	F1—C2—S1	110.4 (3)
O6—S2—O4	110.79 (18)	F2—C2—S1	109.0 (3)
O5—S2—C3	106.3 (2)	F3—C2—S1	109.3 (3)
O6—S2—C3	107.5 (2)	F4—C3—F6	109.9 (4)
O4—S2—C3	99.85 (19)	F4—C3—F5	109.3 (4)
C1—O1—S1	120.0 (3)	F6—C3—F5	109.1 (4)
C1—O4—S2	119.9 (3)	F4—C3—S2	110.3 (3)
O4—C1—O1	107.8 (2)	F6—C3—S2	108.4 (3)
O4—C1—H1	110.1	F5—C3—S2	109.7 (3)

O2—S1—O1—C1	−10.4 (4)	O1—S1—C2—F2	174.9 (3)
O3—S1—O1—C1	−146.1 (3)	O2—S1—C2—F3	170.9 (3)
C2—S1—O1—C1	103.3 (3)	O3—S1—C2—F3	−55.9 (4)
O5—S2—O4—C1	−147.9 (3)	O1—S1—C2—F3	55.0 (3)
O6—S2—O4—C1	−11.6 (4)	O5—S2—C3—F4	−54.8 (4)
C3—S2—O4—C1	101.6 (3)	O6—S2—C3—F4	171.9 (3)
S2—O4—C1—O1	−103.7 (4)	O4—S2—C3—F4	56.3 (4)
S1—O1—C1—O4	−98.6 (4)	O5—S2—C3—F6	65.7 (3)
O2—S1—C2—F1	50.7 (4)	O6—S2—C3—F6	−67.6 (4)
O3—S1—C2—F1	−176.1 (3)	O4—S2—C3—F6	176.7 (3)
O1—S1—C2—F1	−65.2 (4)	O5—S2—C3—F5	−175.3 (3)
O2—S1—C2—F2	−69.3 (4)	O6—S2—C3—F5	51.4 (4)
O3—S1—C2—F2	64.0 (4)	O4—S2—C3—F5	−64.2 (3)

Symmetry codes: (i) −x+1, y−1/2, −z; (ii) x, y−1, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···O2	0.99	2.32	2.803 (6)	109
C1—H2···O6	0.99	2.29	2.802 (6)	111
C1—H1···O3ⁱⁱⁱ	0.99	2.51	3.416 (5)	152
C1—H2···O5^iv	0.99	2.56	3.430 (5)	147

Symmetry codes: (iii) −x+2, y−1/2, −z+1; (iv) −x+1, y−1/2, −z+1.

Ethane-1,2-diyl bis(trifluoromethanesulfonate) (2) top

Crystal data top

C₄H₄F₆O₆S₂	Z = 4
M_r = 326.19	F(000) = 648
Triclinic, P1	D_x = 2.009 Mg m⁻³
a = 10.036 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 10.664 (3) Å	Cell parameters from 3670 reflections
c = 11.276 (4) Å	θ = 2.3–26.3°
α = 83.540 (9)°	µ = 0.60 mm⁻¹
β = 64.178 (9)°	T = 100 K
γ = 89.593 (9)°	Plate, colourless
V = 1078.2 (6) Å³	0.16 × 0.09 × 0.01 mm

Data collection top

Bruker D8 VENTURE diffractometer	4339 independent reflections
Radiation source: TXS rotating anode	3403 reflections with I > 2σ(I)
Helios optic monochromator	R_int = 0.079
Detector resolution: 16 pixels mm^-1	θ_max = 26.4°, θ_min = 1.9°
ω and φ scans	h = −11→12
Absorption correction: multi-scan (TWINABS; Bruker, 2012)	k = −13→13
T_min = 0.564, T_max = 0.745	l = 0→14
4339 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.066	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.166	H-atom parameters constrained
S = 1.07	w = 1/[σ²(F_o²) + (0.0356P)² + 5.6794P] where P = (F_o² + 2F_c²)/3
4339 reflections	(Δ/σ)_max < 0.001
326 parameters	Δρ_max = 0.60 e Å⁻³
0 restraints	Δρ_min = −0.55 e Å⁻³

Special details top

Experimental. Diffractometer operator T. Pickl scanspeed 5-10 s per frame dx 62 mm 1944 frames measured in 7 data sets phi-scans with delta_phi = 0.5 omega-scans with delta_omega = 0.5 shutterless mode

Refinement. Refined as a 2-component twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.7390 (7)	0.7806 (7)	−0.3145 (7)	0.0305 (15)
C2	0.7981 (8)	0.5426 (6)	−0.0952 (8)	0.0330 (16)
H2A	0.902806	0.520173	−0.141213	0.040*
H2B	0.739825	0.497232	−0.130181	0.040*
C3	0.7408 (7)	0.5038 (6)	0.0505 (7)	0.0269 (14)
H3A	0.642752	0.539256	0.098399	0.032*
H3B	0.728878	0.410543	0.069459	0.032*
C4	0.7031 (9)	0.5807 (7)	0.3481 (7)	0.0361 (17)
C5	0.8589 (8)	0.2726 (6)	0.6257 (7)	0.0302 (14)
C6	0.7927 (7)	0.0998 (5)	0.9138 (6)	0.0221 (13)
H6A	0.899447	0.113447	0.889450	0.027*
H6B	0.782152	0.034746	0.862035	0.027*
C7	0.7111 (7)	0.0564 (6)	1.0578 (6)	0.0241 (13)
H7A	0.753362	−0.021922	1.080005	0.029*
H7B	0.605728	0.037346	1.080766	0.029*
C8	0.7390 (8)	0.0661 (7)	1.3534 (7)	0.0357 (17)
O1	0.5416 (5)	0.6374 (4)	−0.1115 (5)	0.0314 (11)
O2	0.6156 (5)	0.8470 (4)	−0.0780 (5)	0.0280 (10)
O3	0.7869 (5)	0.6800 (4)	−0.1208 (5)	0.0273 (10)
O4	0.8474 (5)	0.5512 (4)	0.0961 (5)	0.0271 (10)
O5	0.7148 (5)	0.7467 (4)	0.1546 (5)	0.0293 (10)
O6	0.9481 (5)	0.7020 (5)	0.1759 (5)	0.0378 (12)
O7	0.6265 (5)	0.1192 (4)	0.7537 (5)	0.0321 (11)
O8	0.6023 (5)	0.3478 (4)	0.7861 (5)	0.0294 (10)
O9	0.7323 (4)	0.2186 (4)	0.8829 (4)	0.0220 (9)
O10	0.7222 (5)	0.1561 (4)	1.1360 (4)	0.0269 (10)
O11	0.9608 (5)	0.0795 (4)	1.1190 (5)	0.0321 (11)
O12	0.8618 (5)	0.2776 (4)	1.2118 (5)	0.0358 (12)
F1	0.7956 (5)	0.6816 (4)	−0.3792 (4)	0.0465 (11)
F2	0.6383 (5)	0.8273 (4)	−0.3533 (5)	0.0492 (12)
F3	0.8467 (5)	0.8687 (4)	−0.3484 (4)	0.0440 (11)
F4	0.5908 (5)	0.5129 (4)	0.3503 (4)	0.0496 (12)
F5	0.7841 (6)	0.5051 (4)	0.3855 (5)	0.0506 (12)
F6	0.6486 (6)	0.6642 (5)	0.4320 (5)	0.0556 (13)
F7	0.8389 (5)	0.2819 (4)	0.5157 (4)	0.0397 (10)
F8	0.9190 (4)	0.3805 (4)	0.6300 (4)	0.0357 (9)
F9	0.9521 (4)	0.1820 (4)	0.6202 (4)	0.0363 (10)
F10	0.6861 (6)	−0.0449 (4)	1.3420 (5)	0.0580 (14)
F11	0.6265 (5)	0.1269 (5)	1.4300 (4)	0.0518 (12)
F12	0.8276 (6)	0.0428 (4)	1.4110 (4)	0.0480 (12)
S1	0.65129 (17)	0.73351 (14)	−0.13709 (15)	0.0212 (3)
S2	0.81148 (18)	0.66163 (14)	0.18055 (17)	0.0247 (4)
S3	0.68116 (17)	0.23493 (14)	0.77089 (16)	0.0227 (3)
S4	0.84046 (18)	0.15361 (14)	1.18972 (16)	0.0237 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.026 (4)	0.032 (4)	0.033 (4)	0.000 (3)	−0.014 (3)	−0.004 (3)
C2	0.038 (4)	0.018 (3)	0.055 (5)	0.011 (3)	−0.029 (4)	−0.012 (3)
C3	0.028 (3)	0.017 (3)	0.046 (4)	0.000 (2)	−0.026 (3)	−0.005 (3)
C4	0.047 (4)	0.032 (4)	0.036 (4)	0.000 (3)	−0.025 (4)	−0.002 (3)
C5	0.036 (4)	0.024 (3)	0.032 (4)	0.006 (3)	−0.017 (3)	−0.005 (3)
C6	0.019 (3)	0.016 (3)	0.034 (4)	0.003 (2)	−0.015 (3)	−0.001 (2)
C7	0.021 (3)	0.024 (3)	0.032 (3)	0.000 (3)	−0.016 (3)	−0.001 (3)
C8	0.039 (4)	0.037 (4)	0.035 (4)	−0.002 (3)	−0.020 (4)	−0.005 (3)
O1	0.023 (2)	0.021 (2)	0.051 (3)	−0.0051 (18)	−0.016 (2)	−0.005 (2)
O2	0.027 (2)	0.019 (2)	0.035 (3)	0.0015 (18)	−0.010 (2)	−0.0048 (19)
O3	0.026 (2)	0.023 (2)	0.038 (3)	0.0038 (18)	−0.019 (2)	−0.0024 (19)
O4	0.025 (2)	0.022 (2)	0.042 (3)	0.0004 (17)	−0.022 (2)	0.0003 (19)
O5	0.031 (3)	0.019 (2)	0.043 (3)	0.0054 (18)	−0.021 (2)	−0.0015 (19)
O6	0.032 (3)	0.034 (3)	0.056 (3)	−0.011 (2)	−0.029 (3)	0.002 (2)
O7	0.034 (3)	0.022 (2)	0.049 (3)	−0.0020 (19)	−0.026 (2)	−0.005 (2)
O8	0.028 (2)	0.021 (2)	0.042 (3)	0.0086 (18)	−0.019 (2)	−0.0056 (19)
O9	0.022 (2)	0.016 (2)	0.028 (2)	0.0027 (16)	−0.0114 (19)	−0.0034 (17)
O10	0.029 (2)	0.025 (2)	0.036 (3)	0.0092 (18)	−0.022 (2)	−0.0071 (19)
O11	0.024 (2)	0.034 (3)	0.044 (3)	0.0098 (19)	−0.019 (2)	−0.011 (2)
O12	0.040 (3)	0.026 (2)	0.046 (3)	0.005 (2)	−0.023 (3)	−0.004 (2)
F1	0.055 (3)	0.048 (3)	0.036 (2)	0.008 (2)	−0.018 (2)	−0.015 (2)
F2	0.057 (3)	0.059 (3)	0.045 (3)	0.013 (2)	−0.035 (2)	−0.002 (2)
F3	0.043 (3)	0.037 (2)	0.038 (2)	−0.0109 (19)	−0.008 (2)	0.0069 (19)
F4	0.047 (3)	0.055 (3)	0.037 (2)	−0.023 (2)	−0.012 (2)	0.009 (2)
F5	0.067 (3)	0.036 (2)	0.053 (3)	−0.002 (2)	−0.034 (3)	0.012 (2)
F6	0.072 (3)	0.049 (3)	0.042 (3)	0.005 (2)	−0.020 (3)	−0.007 (2)
F7	0.055 (3)	0.040 (2)	0.026 (2)	0.001 (2)	−0.020 (2)	−0.0021 (17)
F8	0.034 (2)	0.033 (2)	0.036 (2)	−0.0097 (17)	−0.0120 (19)	−0.0011 (17)
F9	0.030 (2)	0.036 (2)	0.032 (2)	0.0125 (17)	−0.0056 (18)	−0.0003 (17)
F10	0.091 (4)	0.040 (3)	0.040 (3)	−0.030 (3)	−0.029 (3)	0.010 (2)
F11	0.040 (3)	0.072 (3)	0.035 (2)	−0.001 (2)	−0.008 (2)	−0.009 (2)
F12	0.072 (3)	0.038 (3)	0.045 (3)	−0.001 (2)	−0.038 (3)	0.006 (2)
S1	0.0196 (7)	0.0175 (7)	0.0266 (8)	0.0005 (6)	−0.0106 (6)	−0.0014 (6)
S2	0.0257 (8)	0.0193 (7)	0.0330 (9)	−0.0026 (6)	−0.0173 (7)	0.0012 (6)
S3	0.0206 (7)	0.0188 (7)	0.0317 (8)	0.0019 (6)	−0.0145 (7)	−0.0024 (6)
S4	0.0251 (8)	0.0184 (7)	0.0301 (8)	0.0030 (6)	−0.0147 (7)	−0.0013 (6)

Geometric parameters (Å, º) top

C1—F3	1.331 (8)	C7—O10	1.489 (7)
C1—F1	1.332 (8)	C8—F11	1.308 (9)
C1—F2	1.337 (8)	C8—F12	1.318 (8)
C1—S1	1.810 (7)	C8—F10	1.342 (8)
C2—O3	1.474 (7)	C8—S4	1.817 (8)
C2—C3	1.493 (10)	O1—S1	1.420 (4)
C3—O4	1.487 (7)	O2—S1	1.416 (4)
C4—F5	1.305 (8)	O3—S1	1.548 (4)
C4—F6	1.311 (9)	O4—S2	1.540 (5)
C4—F4	1.332 (8)	O5—S2	1.423 (4)
C4—S2	1.831 (8)	O6—S2	1.417 (5)
C5—F8	1.318 (8)	O7—S3	1.420 (4)
C5—F9	1.327 (8)	O8—S3	1.421 (4)
C5—F7	1.334 (8)	O9—S3	1.551 (4)
C5—S3	1.828 (7)	O10—S4	1.549 (4)
C6—O9	1.473 (7)	O11—S4	1.417 (5)
C6—C7	1.483 (9)	O12—S4	1.407 (5)

F5···F7	2.823 (7)	F3···F9ⁱⁱ	2.954 (5)
F7···F12ⁱ	2.951 (7)

F3—C1—F1	108.8 (6)	C2—O3—S1	120.5 (4)
F3—C1—F2	108.5 (6)	C3—O4—S2	121.4 (4)
F1—C1—F2	107.9 (6)	C6—O9—S3	121.4 (4)
F3—C1—S1	111.3 (5)	C7—O10—S4	121.4 (4)
F1—C1—S1	110.6 (5)	O2—S1—O1	121.9 (3)
F2—C1—S1	109.6 (5)	O2—S1—O3	108.4 (3)
O3—C2—C3	109.8 (5)	O1—S1—O3	112.0 (3)
O4—C3—C2	108.9 (5)	O2—S1—C1	105.9 (3)
F5—C4—F6	109.2 (6)	O1—S1—C1	107.1 (3)
F5—C4—F4	108.6 (6)	O3—S1—C1	98.9 (3)
F6—C4—F4	108.5 (7)	O6—S2—O5	122.7 (3)
F5—C4—S2	111.3 (5)	O6—S2—O4	105.6 (3)
F6—C4—S2	109.7 (5)	O5—S2—O4	112.3 (3)
F4—C4—S2	109.5 (5)	O6—S2—C4	106.2 (3)
F8—C5—F9	108.6 (6)	O5—S2—C4	106.0 (3)
F8—C5—F7	108.5 (5)	O4—S2—C4	101.8 (3)
F9—C5—F7	108.8 (6)	O7—S3—O8	123.2 (3)
F8—C5—S3	111.2 (5)	O7—S3—O9	112.2 (3)
F9—C5—S3	110.0 (4)	O8—S3—O9	106.4 (3)
F7—C5—S3	109.6 (5)	O7—S3—C5	106.0 (3)
O9—C6—C7	109.1 (5)	O8—S3—C5	105.9 (3)
C6—C7—O10	110.0 (5)	O9—S3—C5	100.5 (3)
F11—C8—F12	108.9 (6)	O12—S4—O11	122.1 (3)
F11—C8—F10	107.7 (6)	O12—S4—O10	107.5 (3)
F12—C8—F10	108.1 (6)	O11—S4—O10	111.9 (3)
F11—C8—S4	112.1 (5)	O12—S4—C8	105.7 (3)
F12—C8—S4	110.2 (5)	O11—S4—C8	106.3 (3)
F10—C8—S4	109.6 (5)	O10—S4—C8	101.1 (3)

Symmetry codes: (i) x, y, z−1; (ii) −x+2, −y+1, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2B···O8ⁱ	0.99	2.62	3.60 (1)	172
C3—H3A···O1ⁱⁱⁱ	0.99	2.60	2.984 (9)	103
C3—H3B···O1ⁱⁱⁱ	0.99	2.59	2.984 (9)	104
C3—H3A···O8^iv	0.99	2.59	3.579 (8)	175
C6—H6A···O6^v	0.99	2.34	3.092 (8)	132
C6—H6A···O11^vi	0.99	2.47	3.034 (8)	116
C6—H6B···O2^vii	0.99	2.45	3.210 (8)	133
C7—H7A···O5^vii	0.99	2.49	3.365 (8)	147
C7—H7B···O7^viii	0.99	2.70	3.525 (7)	142
C7—H7B···O2^iv	0.99	2.54	3.349 (9)	139

Symmetry codes: (i) x, y, z−1; (iii) −x+1, −y+1, −z; (iv) −x+1, −y+1, −z+1; (v) −x+2, −y+1, −z+1; (vi) −x+2, −y, −z+2; (vii) x, y+1, z−1; (viii) −x+1, −y, −z+2.

Acknowledgements

This work was financed by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation). TP thanks the Studienstiftung des deutschen Volkes for a PhD fellowship and associated funding. All authors gratefully acknowledge support from the Fonds der Chemischen Industrie (FCI Sachkostenzuschuss) and the Technical University of Munich (Catalysis Research Center & Graduate School) for financial support. Open access funding enabled and organized by Projekt DEAL.

Funding information

Funding for this research was provided by: Studienstiftung des deutschen Volkes (scholarship to Thomas Pickl); Deutsche Forschungsgemeinschaft (grant No. SPP 1928); Fonds der Chemischen Industrie.

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